Foundation ventilators are advantageous in providing ventilation to crawl spaces beneath houses and elsewhere to circulate fresh air into enclosed areas and prevent rot and decay resulting from dampness. Such ventilators are generally provided with one or more louvers so that the ventilator may be closed in cold weather to prevent undesirable drafts and may be opened in warm weather to circulate fresh air within the enclosed area.
The louvers in such ventilators are generally manually manipulated to open or close the ventilator as desired but there have been several devices known in the prior art for automaticallly opening and closing the ventilators in response to changes in the temperature. Temperature controlled ventilators are shown in U.S. Pat. No. 1,358,193 issued Nov. 9, 1920 to Weston M. Fulton, U.S. Pat. No. 2,975,975 issued Mar. 21, 1961 to Erwin L. Weber, U.S. Pat. No. 3,169,999 issued Jan. 19, 1965 to Frank P. Noll, U.S. Pat. No. 3,368,756 and U.S. Pat. No. 3,436,016 issued in 1968 and 1969, respectively, to Ralph S. Edwards, and U.S. Pat. No. 3,528,606 issued Sept. 15, 1970 to Alvin E. Witten.
The patents to Webber, Noll, Edwards and Witten are all concerned with ventilators particularly intended for use in the foundations of buildings, as in applicant's ventilator. Foundation ventilators are installed in the masonry or brick work of a building foundation and difficulty has been experienced with some of the prior art temperature responsive ventilators because the wet mortar falls on working parts of the ventilator thereby rendering it inoperable for its intended function. Difficulty has also been experienced in certain of the prior art temperature responsive foundation ventilators in maintaining the temperature rsponsive or bi-metallic element in operative relation to the actuating mechanism for the louvers of the ventilator. Some of the prior art temperature responsive foundation ventilators are rendered inoperative by foreign matter and insects becoming entangled in the bi-metallic element and/or the actuating mechanism for the louvers. It is desirable that a ventilator used in the foundation of a building occupy as little of the air space as possible within the opening provided for the ventilator in the foundation wall. In general this type of ventilator comprises a frame, a screen, louvers, and actuating mechanism to open and close the ventilators, and an opening of about 8.times.16 inches (20.times.40 centimeters) or 128 square inches (800 centimeters) is often provided in a foundation wall for a ventilator. It is preferred that the ventilator components occupy only about one-half the open space in the foundation, but the components of at least one prior art ventilator occupy more air space than needed resulting in less ventilation when the louvers are opened.